I have a small matchbox at home, and there' s no matches inside it now; instead within it you will find a varied selection of all the oddments, and things required to replace concertina parts. There's lots of metal ends that fit onto the lever mechanism ( usual on my type of Instrument).. and little tube bits, that cushion the buttons, also tiny screws, thin offcut of brass, and even one prototype alloy button I tried to make, about a decade ago.
If I replace a button then I put the old one in that matchbox; which has proved useful many times when servicing concertina.
Of course if you are unsure do not attempt to service your squeeze box yourself; but for those that can do the basics, I say again keep all those little bits! Don't throw them away.
Look at my matchbox! It's a miniature treasure-trove!!